Abstract: In a digital communications system comprising a plurality of modules plugged into slots, the backplane provides a private five-conductor data bus for each module slot so that data from the modules are transmitted over separate busses. Each of the data busses is split into separately driven branches extending to the right and to the left of its corresponding module, so that the drivers are located at the ends of the branches rather than connected to an intermediate point on a bus. Pairs of slots are connected through the backplane so that, instead of having one module in each slot driving a five conductor data bus, the system can alternatively have a double-bandwidth module in every other slot driving a ten-conductor data bus made up of two five-conductor busses. Clock and synchronization signals provided by control modules are conducted to device modules over separate conductors on the backplane.

Abstract: This invention is a Local Area Network (LAN) which comprises a plurality of NIU's, each arranged to transmit on a separate set of frequencies and to receive on a separate set of frequencies. During operation, a data packet is multihopped from a source NIU, through intermediate NIUs, until reaching an NIU which can transmit a frequency which the destination NIU is capable of receiving. The packet is then forwarded to the destination NIU. The source NIU may also send a control packet and cause the destination NIU to adjust its receive frequency so that subsequent packets may be transmitted directly to the receiving NIU. In an alternative embodiment, the multihopping may be accomplished using specialized headnode modems.

Abstract: A multiplex transmission system, in which a node as a transmission node transmits data frame by frame to a transmission path, and a plurality of other nodes, as reception nodes, returns a reception acknowledgment signal to the transmission path upon proper reception of the frame of data. Each of the reception nodes which properly received the frame returns the reception acknowledgment signal specific thereto to that division of a reception acknowledgment signal area in the frame which corresponds to this node. Each node discriminates the success/failure of signal transmission, by comparing the information registered beforehand in its reception acknowledgment signal table with the information in the reception acknowledgment signal area. When the information of the reception acknowledgment signal table does not coincide with that of the reception acknowledgment signal area, the transmission node re-transmits the frame and the reception acknowledgment signal tables of all the nodes are updated.

Abstract: An add/drop interface is connected in series with a data bus and is constructed for receiving an add/drop module. The add/drop interface includes a data selection multiplexer which receives through data from the data bus and add/drop from the module and selects the proper output data in response to a signal received from a controller in said interface. The controller provides a signal to drive the data selection multiplexer to select the add/drop data only after all transient signals resulting from module connection have dissipated. The controller also provides error checking so that the through data is selected if errors are detected. Timing circuitry in the interface maintains the correct phase relationship between through data and add/drop data.

Abstract: An interface apparatus and method is disclosed which allows communication of digital data messages between a first type of data terminals (10 and 65) employing a message protocol (FIG. 1a) with a "free text-type" message, and other user devices employing other digital message protocols. The invention is adapted to exploit the free text message capability of the first protocol. In accordance with the invention, the incoming user data messages are packed into one or more free text messages of the first message protocol, and conversely "unpack" free text messages from the data terminal employing the first protocol are unpacked and formatted into the message protocol format employed by the user device 65. The invention eliminates the necessity for expensive translation devices which translate the data, and allows a plurality of user data terminals to communicate via a link comprising the data terminals employing the first message protocol.

Abstract: A communication system that provides TDM and FDM communications between communication units. At least two control slots are provided in each TDM frame window to provide communication control information such as channel assignment information.

Abstract: A first switching network embodying the invention is a subscriber installation having a chain structure. In the network, the switching is distributed over a plurality of switches each connecting a terminal to the network. A second embodiment is a business network having a star-chain structure and comprising a plurality of sub-networks of chain type. The sub-networks are star connected to central switches which operate in a load sharing mode. According to the method embodying the invention, the terminals connected to the network assume themselves the responsibility for determining communication routes through the network. During a communication set-up phase, caller and callee terminals transmit call packets which are disseminated to all terminals in order to measure two so-called "distances" respectively between the caller and the callee and between the callee and the caller. These distances are after included in data packets for routing said packets.

Abstract: An adaptive TDMA (time division multiple access) communication system is illustrated which dynamically maintains potentially different frequencies between nodes of the communication system using a process of communicating the quality of received signals between the nodes and storing this information so that an optimum frequency band can be selected whereby whenever signal quality deteriorates, an alternate frequency can be selected to provide continued communications. An embodiment of the system spans both high frequency (HF) and very high frequency (VHF) to establish the communications through atmospheric induced refractions (reflections) beyond line of sight between directly communicating nodes of the system. Further, the system uses frequency hopping both for signal transmission security and for node identification. When a node is traffic idle and also on a periodic maintenance basis, frequency bands other than the traffic frequency are analyzed for potential future use.

Abstract: A communication network is provided for transmitting data in a hostile electromagnetic environment. Master and slave units are coupled to a data path by transformer coupling. The slave units can be turned on by applying a DC voltage between transfomer taps at the master, and detecting the voltage at corresponding taps at the slave. Separate pairs of conductors are used to carry signals transmitted by the master and signals transmitted by the slave. The conductors form a closed loop data path enabling the master to selectively transmit data either in a clockwise or counterclockwise direction around the loop. Data may also be received by the master either clockwise or counterclockwise around the loop. In this manner, the master can communicate with the slaves even if there is a break in the data path.

Abstract: The invention relates to a switching module for asynchronous time multiplex comprising at least one junction switch for transmitting packet-switched information from one bus (14) to another bus (16). The junction switch comprises a translation memory (9) for translating packet addresses into new addresses, a comparator (10) for selecting the packets that are to be routed to another bus, a queue memory (12) for storing selected packets until an insertion circuit places the selected packets into the queue memory (12) on the other bus (16). With the aid of a such junction switch, a flexible network structure can be realized, the traffic of packets on the different buses can be mutually asynchronous and virtual circuits can be realized with the aid of the translation memory (9).

Abstract: A code division multiplex system for use in a spread spectrum communication system utilizes selectable length spread spectrum spreading code sequences. At the encoder, one of a pluraluty of a spread spectrum spreading code sequences having a given fixed length is selected for differential encoding in accordance with the input data to be transmitted. At the receiver correlator, a selectable length differential decoder is set to be responsive to a spread spectrum spreading code sequence having a length substantially equal to the length of the encoded spread spectrum spreading code sequence.

Abstract: In a system interconnecting a LAN and an ISDN to which data terminals of the LAN are accessible through a common interface, a network-to-terminal LAPD packet is transmitted from the interface to the data terminals, containing a TEI value of group address, a destination address of a group address of the data terminals and an action indicator set to an assigned TEI value. The data terminal specified by the assigned TEI value transmits a packet containing the address of the interface and a TEI value equal to the assigned TEI value. In addition, the interface creates a table describing a relationship between a TEI value and a source address both contained in a terminal-to-network LAPD packet. An address stored in the table is recalled in response to a TEI value contained in an LAPD signal from the network and entered to this LAPD signal as a destination address to form a network-to-terminal LAPD packet for transmission to the data terminals.

Abstract: A two-way CATV system, in which a plurality of communication channels are set simultaneously in an upstream communication line between a plurality of end terminal equipment and a center equipment by using frequency division multiplexing, is disclosed. A digital transmultiplexer is arranged at each junction between a trunk line and a branch line for converting a frequency division multiplex signal into a time division multiplex signal. Frequency division multiplex signals from the terminal equipment are converted into time division multiplex signals, and then only a time slot corresponding to a frequency slot containing a signal therein is picked up to thereby prevent upstream noises from flowing into the trunk line.

Abstract: A multiplex communication system includes a plurality of exchanges and multiplex communication apparatuses connected to at least one exchange through a plurality of lines. Each of the multiplex communication apparatuses comprises first registers for storing first selection number information from the lines and second registers for fetching and storing second selection number information from an associated one of the exchanges, and is arranged such that a CPU of the associated communication apparatus determines that the exchange is to perform its interrupting operation and causes encoders and decoders to be switched to their through mode when the first selection number information stored in the first registers coincides with the second selection number information stored in the second registers.

Abstract: To the switching node belongs at least one coupling element which has n input lines and n output lines optionally connectable to them via a space switch. To each of the input lines a buffer store is assigned in which k data packets are storable and which has m.ltoreq.k output terminals via which m data packets are simultaneously suppliable to the space switch having m.times.n input terminals and n output terminals. The storage addresses, under which the data packets to be routed are stored in the individual stores, are stored in accordance with the address signals contained in the data packets and stored in queue buffer stores assigned to the output lines. The queue buffer stores are cyclically accessible by a central control device for making available storage addresses. On the basis of storage addresses made available in such manner the central control device, on the one hand, controls the setting of the space switch and, on the other hand, the output of data packets from the buffer stores.

Abstract: Data bits are decoded from a composite signal that is formed by coding multiple bit sequences with respective spreading codes, and transmitting the coded bit sequences simultaneously and asynchronously over a single channel in which the bit sequences are added. This decoding involves a metric in combination with a repetitive decision process which is only linearly dependent on the number of bit sequences in the composite signal.

Abstract: A non-reciprocal bidirectional duplexer includes a first transmission medium extending from a first terminal to a third terminal; a second transmission medium extending from the second terminal to the third terminal; and a plurality of non-reciprocal, bidirectional phase shifting elements, coupling the transmission mediums and spaced along them; each of the phase shifting elements includes means for amplifying a signal in a first direction from the first to the second transmission medium and for amplifying a signal in the second direction from the second to the first transmission medium; and means for establishing a phase differential between the signals moving in the first and second directions.